This is usually due to another application running in the background. Most of the time it's something like Discord's in-game overlay, or Steam's in-game overlay. Try disabling those if you have Discord open or if you are running osu! through Steam.

Your Windows cursor should not appear over your game even if you are not using your desktop's resolution or playing with fullscreen.

Death wrote:

This is usually due to another application running in the background. Most of the time it's something like Discord's in-game overlay, or Steam's in-game overlay. Try disabling those if you have Discord open or if you are running osu! through Steam.

Your Windows cursor should not appear over your game even if you are not using your desktop's resolution or playing with fullscreen.